Comprehensive analysis on the in-situ ash fusibility and mineral reactions of ash mixtures in the co-gasification process

Abstract

Biomass can effectively modify coal ash fusibility and alleviate several operational issues like agglomeration, sintering, and erosion for slagging gasifiers. The key issue is to clarify the ash fusion properties and mineral transformation during the heating process. The fusion temperatures, mineral evolutions, in-situ morphology observation and thermodynamic analysis of the coal, biomass and biomass-coal blended ash samples were systematically evaluated in this paper. The ash fusion temperatures (AFTs) presented V-type curves with the increasing rape straw ratio. Then the bottom point occurred at the ratio of 50 wt% due to the reduction of refractory minerals (mullite, quartz, < 50 wt%; kalsilite, oldhamite, >50 wt%) and the increase of low-melting-point minerals and their eutectics (leucite and anorthite). Besides, the thermodynamic calculation can provide the basis for the prediction of ash fusion behavior. The in-situ morphology evolutions of blended ashes further revealed the relationship between ash fusion behaviors and morphological changes. Namely, the terminative sintering and melting temperature were highly related to the ash deformation temperature and flow temperature, R2 was 0.9901 and 0.9846, respectively. The significant work could guide the mixing conditions during the co-gasification of high‑silicon‑aluminum coal and biomass and improve the ash fusion properties.